In the prior art, the slag flowing out of a shaft furnace, e.g. a blast furnace, is quenched by means of water jets emerging from nozzles in such a way that the liquid slag turns into a more or less fine slag sand. So that this slag sand can be used further in a profitable manner, the mixture of slag sand and water known as the slag mash, which results from the said spraying must as far as possible be dewatered.
According to the prior art, this dewatering takes place without exception by wall sections of a receptacle for the wet slag sand being designed as filtering surfaces permeable to water. To this end, the vertical side walls, for example of a cylindrical receptacle, can be designed entirely or partly as filter surfaces, or even only the conical outlet area of such a receptacle.
In the first case, the filtering surfaces can be designed to be relatively large, but the portion of slag sand located in the bottom, e.g. conical, outlet is left without being dewatered; whereas in the second case, dewatering of this portion certainly takes place, but the filtering surface remains relatively small. In both cases, but especially in the last mentioned case, the filter surfaces are exposed to high mechanical compressive stress from the contents of the receptacle so that these filter wall sections must be of appropriately resistant, that is expensive, construction.
A particularly serious disadvantage of both constructions (or a combination of the two) consists in the fact that the said filter surfaces become clogged by slag sludge after relatively short use and thus become ineffective. To remove the sludge from the filter surfaces, injection of water, for example by means of nozzles, from outside through the filter surfaces toward the interior of the receptacle is known in the prior art.